My truck has recently developed a metallic clicking from the front left wheel (as best as I can tell). I only hear it at slow speeds and it seems to start during turns. I originally thought it was a rock in the tire because I could only hear it with the windows down. The sound has progressed to something more metallic and I have checked for rocks in tire several times. Any ideas of what it could be, and how to troubleshoot it would be greatly appreciated.
Have you checked to see if any of the lug nuts are loose?
First thing to check is your front wheel bearings. Your truck should use tapered roller bearings (I believe they didn’t change this until 2004 with the new body style and six lug wheels), which are cheap and easy to service/replace. Any mechanic with plenty of gray hair will know exactly what to do here. If they’re making a lot of metallic noise now, it may be too late to simply repack them and the bearings and races may need to be replaced (easy), but worst case scenario might run you $100 unless it’s worse than you describe and the spindle is trashed.
Broken or missing anti-rattle springs on the caliper is a likely cause.